STRANGER Manga

ストレンジャー; 异乡人; 異鄉人; 陌生人

As the town’s sheriff, Fran was on an errand for his people. Alas, on his journey back, his horse died. Stranded in the middle of a desert with his only transport to civilization dead to the world, Fran had to endure scorching heat to reach his town. Wandering for days, his weakened body betrayed him, only to be saved by a Native American…

Summary from Canna (that’s originally in English):

Fran used to engage in murders and robberies.
He now shows remorse for those illegal dealings, and works as a sheriff in a small town.
He lost his pony and wanders in the wilderness asking himself,
“Is this a return of my past misdeeds?”

The series Stranger has been licensed, it is not available in Manga Fox.